ig26 



HUMAN ANATOMY. 



glass as minute openings on the mucous membrane. The former, the intramucous 

 glands, are simple in structure, consisting usually of a single alveolus, less frequently 

 of two or three, from .070-. loomm. in diameter. They are lined with cylindrical 

 epithelium and occur in all parts of the urethra, being most numerous in the spongy 

 portion (Herzog). The submucous glands, although small, are larger than those 

 limited to the mucosa, but are less widely distributed, being absent in the distal half 

 of the pars membranacea and the proximal third of the spongy portion. They are 

 most abundant and best developed on the upper wall of the spongy portion, anterior 

 to the openings of the ducts of Cowper's glands (Herzog). Their ducts often extend 

 several millimetres obliquely backward, more or less parallel to the urethra, and divide 

 into two or more slightly expanded terminal tubules which are lined with cylindrical 

 epithelium. Where surrounded by the corpus spongiosum, the submucous glands lie 

 embedded within the fibrous tissue of the albuginea ; in the pars membranacea the 

 glands are surrounded by the bundles of the compressor urethrae muscle. 



In addition to the foregoing true, although small glands, the urethral mucous 

 membrane is beset, along its upper wall and near the mid-line, with small diverticula 

 (lacunae urethrales) which are little more than tubular depressions within the lining of 

 the canal and cannot be regarded as glands, although they often receive the ducts of 



submucous glands that 

 Fig 1635. open into them. One of 



exceptional size (from 4- 

 12 mm. in length) is com- 

 monly found on the roof 

 of the navicular fossa, its 

 orifice being guarded by 

 a fold of mucous mem- 

 brane (valvula fossae na- 

 vicularis). 



The Fe7nale Urethra. 

 — As in the male, the wall 

 of this canal consists es- 

 sentially of a mucous 

 membrane supplemented 

 by an outer muscular tu- 

 nic. The mucous mem- 

 X 50. brane, thrown into longi- 



tudinal folds when the 

 canal is closed, is composed of a tunica propria, rich in elastic fibres, covered with 

 stratified squamous epithelium that above resembles the vesical type and below that 

 of the vestibule. In the female the urethral glands are represented by small groups 

 of tubular alveoli that open by minute orifices on the mucous surface and correspond 

 to Littr^'s glands in the male. They are most plentiful in the upper part of the ure- 

 thra, and often, especially in aged subjects, contain concretions resembling those 

 found in the prostatic tubules (Luschka). The mucosa is also beset with small pit- 

 like depressions, similar in character to the lacunae in the male, into which the ducts 

 of the glands frequently open. 



The muscular tissue of the female urethra comprises intrinsic unstriped fibres 

 forming part of the wall and extrinsic striated tissue outside of the canal. The 

 former are represented by an inner layer of longitudinally disposed fibres and an 

 outer one of circular bundles, the two being separated by an intervening stratum of 

 areolar tissue on which a rich venous plexus confers the character of erectile tissue. 

 At the internal orifice the circular fibres, in conjunction with those from the trigone, 

 form the internal vesical sphincter. Between the layers of the triangular ligament the 

 canal is surrounded by bundles of the compressor urethrae, fibres of which are pro- 

 longed into the anterior vaginal wall. The lower end of the urethra is embraced by 

 the anterior fibres of the sphincter vaginae muscle (Lesshaft). 



Vessels. — The arteries supplying the urethra are from several sources, since 

 those distributed to the canal are usually branches derived from the vessels passing 

 to the surrounding organs. The pars prostatica receives twigs from the middle hem- 



Surface 

 epithelium 



Crypts 



Tunica 

 propria 



Longitudinal 

 muscle 



Circular 

 muscle 



Longitudinal section of wall of female urethra. 



